LO4 -Abdominal Wall
4. Understand the basic structure and contents of the inguinal canal.
The inguinal canal allows passage of certain structures, and importantly the descent of the testes during development. It consists of an anterior (oblique mm. aponeuroses) & posterior wall (transversalis fascia and aponeuroses), roof (transversalis fascia and aponeuroses), and floor (inguinal ligament).
The inguinal ligament extends from the anterior superior iliac spine (ASIS) to the pubic tubercle. It is the inferior extent of the external oblique aponeurosis.
The ‘entrance’ or internal aperture of the canal is the deep inguinal ring. It is through this area that the round ligament of uterus or spermatic cord enters the inguinal canal. The deep ring is an invagination of the transversalis fascia. Indirect inguinal hernias enter the inguinal canal through the deep inguinal ring.
The ‘exit’ or medial aperture of the inguinal canal is the superficial inguinal ring, formed by the external oblique aponeurosis. It also transmits the round ligament of uterus, or spermatic cord. The margins of the superficial inguinal ring are the medial crus (attaching to the pubic symphysis) and the stronger, lateral crus (attaching to the pubic tubercle).
Major contents of the inguinal canal include:
- Round ligament of uterus
- Spermatic cord
- Ilio-inguinal n.
- Vasculature & lymphatics
The round ligament (of uterus) is a remnant of the gubernaculum, connecting the uterus to the labium majus. The round ligament presents as a tubular collection of adipose tissue.
The spermatic cord contains the cremaster m., cremasteric a., testicular a., ductus deferens, artery of ductus deferens, pampiniform venous plexus, genital br. of the genitofemoral n., sympathetic nerve fibers, and lymphatic vessels.
The ilio-inguinal n. (branch of L1 VPR) is located superficial to the round ligament of uterus or spermatic cord in the inguinal canal, and will exit the superficial inguinal ring as either the anterior labial/scrotal brs. These are sensory branches that innervate skin of the medial thigh, and either the mons pubis & labium majus, or root of the penis.